Anthropocene?

By David Kattenburg

At the planetary level, Earth has gone through countless changes of its own since it coalesced out of a cloud of dust some 4.5 billion years ago. It took half a billion years for Earth to cool to the point where liquid water forms, and things have been changing every since.

Paul Hirt

Tectonic plates jostled and buckled. Continents moved this way and that, crashing into each other, piling skyward vast mountain belts that then got ground down to seabed. Volcanoes belched colossal plumes of dust and debris into the atmosphere. The atmosphere warmed and cooled.

Now and then, huge masses of iron, nickel and other debris plowed into Earth’s crust, gouging out huge craters, muddying the atmosphere and wiping out life on biomass scale.

Each time life recovered, reinventing itself in an improbable sequence of experiments: discovering oxidative respiration and photosynthesis, eukaryosis and multicellularity; crawling from water to land; growing incredibly huge, or excelling at being tiny; staking out niches; establishing cooperative networks.

Andrew Weaver

Then came humans. For hundreds of thousands of years, Homo sapiens wandered Earth’s landscape in small numbers, with little impact. This would change with the discovery of agriculture, leading to sedentary lifestyles and urban centers drawing on the capacity of surrounding land.

Still, for many, many years, human communities were small and far between. By 1800, when the industrial revolution was just beginning to pick up steam — just a couple hundred years ago — only a billion humans inhabited the planet. In the happy years between World War One and Two, the number sat at about 2 billion, doubling to four by 1974, then doubling each decade since then.

Today, with a human population of 7.4 billion, it seems our species is transforming the planet on a hitherto unimaginable scale. In a recent report published in Science Magazine, a battery of researchers announced that humans have actually heralded in a new geologic “Epoch” — the “Anthropocene.” The age of humans.

David Schindler

The list of human-induced changes to Earth’s atmosphere, oceans, land surface and crust is incredibly lengthy. Among the most prominent components of the geological stratum humans have laid down — at a particularly high rate since about 1950 — are aluminum, plastic, and concrete. The radioactivity from atmospheric nuclear tests conducted by the US, the Soviets, Chinese and French is another readily identifiable signature. Sediments associated with the proposed Anthropocene contain particularly high levels of nitrogen and phosphorus, both agricultural in origin.

Of course, over the past couple hundred years, humans have released vast quantities of carbon dioxide and methane into the atmosphere, transforming the planet’s exquisitely complex climate system. And by appropriating an astonishing quarter of Earth’s net productivity, humans have wiped out other species on a scale rivaling Earth’s most brutal extinction events.

The Anthropocene has its critics, both within and outside the scientific community. Why single out the human species for all this destruction and waste, some ask, when it’s really a set of economic doctrines — developed and guided by a tiny, tiny fraction of Earth’s 7.4 billion human inhabitants — that are to blame. Chief among these, the belief that human economic growth can go on forever; that Earth’s resources are finite. The controversial belief that the challenges posed by humanity’s glaring transformation of the planet can be addressed through geoengineering.